Mechanical deformation, bone

The similarities between the cytoplasmic processes of bones cells and the stereocilia of hair cells are that they both (1) measure mechanical deformations (vibrations of a fluid domain), (2) communicate their measurement to a network, (3) do this with dendritic structures, (4) the dendrites of both cells are constructed of similar materials (e.g., actin and fimbrin) and (5) the initial signaling in both cases consists of opening ion channels. While the hair cells communicate their information to a network that feeds to the brain, the bones cells connect to a lower level network (CCN) with (potentially) local decision-making software. 

Bone resorption in response to continuous mechanical deformation appears to be regulated by cells of osteoblast lineage such as preosteoblasts, osteoblasts, bone lining cells and osteocytes, and stretch-enhanced, osteoclastlike cell formation involves prostaglandins, but not PGE2 (Soma et al., 1996). Stretch-induced increases in osteopontin and osteonectin were inhibited by addition of the calcium channel antagonist nifedipine suggesting an important role for L-type calcium channels in early mechanical strain transduction pathways in osteoblasts. 

Calvacanti E A, Shapiro 1 M, Composto R 1, et al. (2002) RGD Peptides immobilized on a mechanically deformable surface promote osteoblast differentiation. 1 Bone Min Res 17 2130-2140... 

Deformation mechanisms in bone matrix at the nanoscale contribute to its exceptional mechanical properties, as... 

Figure 15 Nanoscale deformation mechanisms in bone, (a) Fibrils stretch with increasing tissue strain up to around the elastic/inelastic transition point, then approach a constant value, (b) Nanometer-level model for the deformation in mineralized collagen fibrils and extrafibrillar matrix. Reproduced with permission from Gupta, H. S. Wagermaier, W. Zickler, G. A. etal. Nano Lett. 2005, 5,2108-2111. ° Copyright 2005 American Chemical Society.

Yerramshetty, J.S., Lind, C., and Akkus, O. (2006) The compositional and physicochemical homogeneity of male femoral cortex increases after the sixth decade. Bone, 39 (6), 1236-1243. Donnelly, E. et al. (2010) Effects of tissue age on bone tissue material composition and nanomechanical properties in the rat cortex. J. Biomed. Mater. Res. A, 92 (3), 1048-1056. Donnelly, E. et al (2010) Contribution of mineral to bone structural behavior and tissue mechanical properties. Calcif. Tissue Int., 87 (5), 450—460. Pathak, S. et al (2012) Assessment of lamellar level properties in mouse bone utilizing a novel spherical nanoindentation data analysis method. J. Mech. Behav. Biomed. Mater., 13, 102—117. Burket, J.C. et al (2013) Variations in nanomechanical properties and tissue composition within trabeculae from an ovine model of osteoporosis and treatment. Bone, 52 (1), 326-336. Carden, A. et al (2003) Ultrastructural changes accompanying the mechanical deformation of bone tissue a Raman imaging study. Calcif. Tissue Int., 72 (2), 166-175. 

The capacity of hard tissue such as bone to generate potentials in response to mechanical stress has been known from the beginning of the nineteenth century. A piezoelectric theory to account for the electric potential observed in dry bone on deformation was proposed by Fukada and Yasuda in 1957 and subsequently explored by many others in the 1950s and 1960s as well as by Friedenberg et al. in 1971. 

A representative stress-strain curve of one of the PDMS-CaO-Si02 nano-hybrids is shown in Figure 11.7, in comparison with that reported for human cancellous bone [29]. Unlike the usual brittle ceramics, the nano-hybrid was deformable and showed mechanical properties analogous to those of human cancellous bone. 

In light of the increased number of man-6-P/IGF-II receptors in I-cell fibroblasts, the above interactions of IGF could have far-reaching effects. For example, I-cell disease has not been typically associated with abnormalities in phos-phorous/calcium metabolism. The extensive skeletal deformities could involve impairment of mechanisms of orderly calcium deposition. Rather than resulting from a primary disorder of calcium metabolism, it is possible that the bone lesions in I-cell disease are secondary to altered lysosomal processing events in the kidney or liver. 

Tribasic calcium phosphate is widely used as a capsule diluent and tablet filler/binder in either direct-compression or wet-granulation processes. The primary bonding mechanism in compaction is plastic deformation. As with dibasic calcium phosphate, a lubricant and a disintegrant should usually be incorporated in capsule or tablet formulations that include tribasic calcium phosphate. In some cases tribasic calcium phosphate has been used as a disintegrant. It is most widely used in vitamin and mineral preparations as a filler and as a binder. It is a source of both calcium and phosphorus, the two main osteogenic minerals for bone health. The bioavailability of the calcium is well known to be improved by the presence of cholecalciferol. Recent research reports that combinations of tribasic calcium phosphate and vitamin D3 are a cost-effective advance in bone fracture prevention. ... 

Joint degeneration is the end-stage of a process of destruction of the articular cartilage, which results in severe pain, loss of motion, and occasionally, an angular deformity of the extremity [Buckwalter et al., 1993], Unlike bone, cartilage has a very limited capacity for repair [Salter, 1989]. Therefore, when exposed to a severe mechanical, chemical, or metabolic injury, the damage is permanent and often progressive. 

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